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The need: I'm trying to filter a custom post type archive using a GET parameter, so that I can split the posts in two groups depending on which terms they are tagged with.

How: So far I've decided to use the pre_get_posts hook, altering the query when the archive for this custom post type is rendered.

The problem: The code I'm using is not working. I can't seem to find the issue, but it is definitely not working. Maybe someone who has more exp with this hook may tell me what I'm missing:

function event_type_filter( $query ) {
    if ( is_post_type_archive( 'event' ) ) {

        if ( isset($_GET["event_term"]) ) {
            $tipo_de_curso = $_GET["event_term"];
            if ( $tipo_de_curso == "singleclass" ) {
                $query->set( 'cat', '1,2,3,4' );
            }
            if ( $tipo_de_curso == "course" ) {
                $query->set( 'cat', '-1,-2,-3,-4' );
            }
        }
    }
return $query;
}
add_action('pre_get_posts','event_type_filter');

Here in the Codex they recommend a similar approach, and I can't spot the differences, but sure there has to be some. There is some questions in this site about this hook that should serve as a model, but I didn't see how to adapt to my case.

Any ideas? Thanks :)

  • 1
    tried removing return $query; ? – Reigel Feb 18 '15 at 9:08
  • also on your if statement if ( is_post_type_archive('event') && ! empty( $query->query['post_type'] == 'event' ) – Reigel Feb 18 '15 at 9:12
  • removing the return $query; does not have an effect, but neither had the addition, to begin with. (I already tried with and without it.). Also, I completed the if statement, but I cant notice any changes. Thanks @Reigel – versvs Feb 18 '15 at 10:11
  • 1
    Depending on the URI is_post_type_archive() may fail - See the Notes section in the Codex. Perhaps replace if(is_post_type_archive('event')) with if(get_query_var('event'))? – David Gard Feb 18 '15 at 10:46
  • 2
    FYI, when you use and action hook (add_action()), the function that you reference doesn't need to return anything. On the other hand, if you are using a filter hook (add_filter()) then you do need to return a value. So in your case the line return $query; is superfluous - it's not causing your code to fail, but you don't need it. – David Gard Feb 18 '15 at 10:50
2

You should be using methods of the $query instance instead of the is_* template tags. And are the categories you are trying to filter a custom taxonomy? cat only works on the default category taxonomy:

function wpse_178500_event_type_filter( $wp_query ) {
    if ( ! empty( $_GET['event_term'] ) && $wp_query->is_main_query() && $wp_query->get( 'post_type' ) === 'event' ) {
        $tipo_de_curso = $_GET['event_term'];

        if ( ! $tax_query = $wp_query->get( 'tax_query' ) )
            $tax_query = array();

        if ( $tipo_de_curso === 'singleclass' ) {
            $tax_query[] = array(
                'taxonomy' => 'category', // Make sure this is correct! "category" is the default post category.
                'field' => 'term_id',
                'terms' => array( 1, 2, 3, 4 ),
            );

        } elseif ( $tipo_de_curso === 'course' ) {
            $tax_query[] = array(
                'taxonomy' => 'category', // Make sure this is correct! "category" is the default post category.
                'operator' => 'NOT IN',
                'field' => 'term_id',
                'terms' => array( 1, 2, 3, 4 ),
            );
        }

        $wp_query->set( 'tax_query', $tax_query );
    }
}

add_action( 'pre_get_posts','wpse_178500_event_type_filter' );
  • You nailed it. I was trying to filter terms in a custom taxonomy. Your code works like a charm. I wonder: Is this the only way to achieve this on custom taxonomies? – versvs Feb 18 '15 at 11:17
  • 1
    You can use taxonomy => term_slug, but that's about it. tax_query is almost always the way to go. – TheDeadMedic Feb 18 '15 at 11:20

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